1. Technical Field
The present invention relates to a mask, a film forming method, a light-emitting device, and an electronic apparatus.
2. Related Art
An organic EL element has a configuration in which a light-emitting layer including at least a fluorescent organic compound (light-emitting material) is disposed between a negative electrode and a positive electrode. The organic EL element generates excitons by injecting electrons and holes into the light-emitting layer, the electrons and the holes are then recombined, and light (fluorescence/phosphorescence) is emitted when the exciton activity decreases.
The organic EL element has characteristics that it can perform surface emission with a high brightness in the range of 100 to 100,000 cd/m2 at a low voltage of 10V or less and that it can emit blue to red light in accordance with the light-emitting material used. The organic EL element has attracted attention as an element to be provided in a display device (light-emitting device) which can realize a large-area full color display at low cost.
An example of such a light-emitting device is a passive matrix light-emitting device shown, for example, in JP-A-8-315981. In the passive matrix light-emitting device, a plurality of positive electrodes and negative electrodes having a linear shape are disposed opposite to each other in a matrix and organic semiconductor layers are individually disposed between the electrodes so as to correspond to positions where the electrodes intersect each other. By controlling switching between ON and OFF states of the electrodes intersecting each other, the organic semiconductor layers individually disposed can be allowed to independently emit light, thereby realizing the full color display.
Here, in the light-emitting device, the negative electrodes, the organic semiconductor layers, and the negative electrodes are generally stacked in this order. The linear negative electrodes are formed by defining insulating partition walls disposed on a substrate before forming the negative electrodes.
The partition walls are mainly formed of a photosensitive resin material and contain moisture or the like due to a photolithography method used to form the partition walls. Accordingly, there is a problem that the organic semiconductor layers reform and deteriorate due to the moisture or the like with the lapse of time and characteristics of the organic EL element such as emission efficiency deteriorate.
A method of forming a negative electrode by the use of a vapor deposition method such as a vacuum deposition method using a shadow mask (hereinafter, simply referred to as “mask”) having an opening corresponding to the shape of a linear negative electrode without forming the above-mentioned partition walls is known as a method for solving such a problem.
When the mask having an opening corresponding to the shape of the negative electrode is formed, a warp or a twist is formed in the opening due to a decrease in the rigidity of a mask substrate. Accordingly, the negative electrode formed using the mask also has a warp or a twist, the shape of which is similar to that of the opening. As a result, the characteristics such as the emission efficiency of the organic EL elements of a light-emitting device are not uniform.
Such a problem occurs similarly, for example, when a plurality of narrow metal interconnections arranged in parallel to each other are formed in a bundle using a vapor deposition method.